The present invention relates to footwear and, more particularly, to an adjustable footwear sole construction and method for making the same.
The design and manufacture of footwear is complicated by the fact that different people have different footwear needs. For example, some individuals prefer a firmer, more unyielding sole, while others prefer a softer, more cushioning sole. With some people this is simply an aesthetic desire, but for others it can result from physical factors, such as those associated with foot shape, skeletal alignment and other anatomical issues. Anatomical issues cause some individuals to suffer from a tendency to pronate (roll their feet inward when striding) and others to have the opposite tendency to supinate (roll their feet outward when striding). One method for addressing these issues is to stiffen the sole in select regions to provide increased resistance against the undesired motion. For example, pronation can be addressed by providing a dual-density midsole with a higher density region along the medial side of the sole. Similarly, supination can be addressed by providing a dual-density midsole with a higher density region along the lateral side of the sole.
In an effort to address the needs of different consumers, a variety of footwear products have been developed with a customizable sole construction. For example, in some products, the sole defines a void or receptacle adapted to receive one of a variety of different cushioning inserts, or a single insert having differing cushioning characteristics depending on the position of the insert in the receptacle. The wearer customizes the sole based on the wearer's individual cushioning and support needs by either inserting the appropriate cushioning insert into the receptacle or rotating the single insert to the desired position. A type of cushioning insert configuration is described in U.S. Patent Publication 2008/0289219, which is hereby incorporated herein by reference in its entirety.
There is also an ongoing effort in the footwear industry to produce footwear that provides both durability and flexibility. Many conventional footwear constructions, however, focus on either durability or flexibility—but usually not both—because the features providing these characteristics typically compete against one another. One construction that is known for flexibility is a direct attach construction, which can include a flexible polyurethane midsole that is direct attached to an upper. The direct attach construction also provides a secure connection between the midsole and the upper and eliminates the need for cement or a welt. One typical method for manufacturing a direct attach construction includes arranging the upper over a last and adding a sole board adjacent a bottom surface of the last to provide a molding surface. The assembly is then placed in a mold so that the midsole material can be molded in place directly onto the sole board and upper.
While the customizable sole and the direct attach constructions are both desirable, it is difficult to combine the two constructions in one piece of footwear.